#include<stdio.h>
char* mystrstr(const char* a,const char* b)
{
    char* s1=NULL;
    char* s2=NULL;
    char* cur=a;
   while(*cur)
   {
    s1=cur;
    s2=b;
    while(*s1==*s2&&*s2!='\0')
    {
        s1++;
        s2++;
        if(*s2=='\0')
        {
            return cur;
        }
    }
    cur++;
   }
   return NULL;
}
int main()
{
   char a[]="asdgfh";
   char b[]="dg";
  char* ret= mystrstr(a,b);
  printf("%s",ret);
    return 0;
}